Method of cold-dishing sheet metal



H. McCABE;

I METHOD OF COLD DISHING SHEET METAL.

APPLICATION FILED 1ULY3, I919.

Patented J uly 5, 1921.

UNITED STATES HUGE noon 1m,

OF LAWRENCE, MASSACHUSETTS.

METHOD 01' COLD-DISHING SHEET METAL.

To all whom it may concern:

Be it known that I, HUGH MoCABE, a citizen of the United States,-re'siding at Lawrence, in the county of Essex and State of 7 the other hand pressure in a dished rather than have invented certain new and useful Im rovements in Methods of Cold-Dishin S eet Metal; and I do hereby declare t e following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same. 7

This invention relates to a method of cold dishing sheet metal. The invention has for an object to provide a method for cold dishing sheet metal in which the dish is formed in successive incremental steps. The invention consists in the method hereinafter described and particularly defined in the claims.

In the drawing, Figure 1 represents a portion of the preferred machine in which a metal sheet is dished according to the present method; Fig. 2 is a plan of a portion of a circular plate illustrating diagrammatically the different portions of the plate which are successively depressed; Fig. 3 is an elevation of the plate after being dished.

It is well recognized in boiler shop practice that for some purposes it is very advantageous and desirable to use sheet metal in dished instead of flat form. Whenever the particular piece of sheet metal is to be subjected to pressure as for example the heads of boilers, it is well known that a steel plate of given thickness will withstand much more flat form. The method usually employed for dishing metal plates for t is pur ose consists in heating the plate in a m e furnace to a red heat and then forming the dish in one operation in a very heavy dishing press while the metal is hot. This method of forming dished plates obliges the ordinar oiler man' to either order the plates directly from the mill in dished form or on to ship the flat late back to the mill to have it dished. bviously, either procedure makes the cost of the dished plate exceedingly high and furthermore, often delays construction. For instance, the expense of shipping back a circular steel bo1ler plate to the mill and havingrit dished amounts to approximately $60. he present method ellminatesthe disadvantages of the former methods and contemplates per- .assachusetts,

Specification of Letters Patent. Application filed July 3, 1919. Serial No.

- nut 13. The

v diameter of Patented July 5, 1921. 808,514.

dished plates in op and with equipmitting the formation of the ordinary boiler sh ment which is usually found in such sho s, at a very small fraction of the expense WhlOh would otherwise be incurred.

In Fig. 1 a portion of a press or similar machine is shown, having the usual reciprocating head 10 which may be reciprocated at the will of the operator by usual and well known revisions not shown. The reciprocating ead 10 is provided with a ram 12, screwed therein and which is adjustably held in a locked position with relation to the reciprocating head 10 by a lock ram 12 is cylindrical in shape, and is provided with threads 14 which cooperate with corresponding threads in the reciprocating head and of such size that there are four threads to the inch. It will be observed that the ram 12 may be lowered from the reciprocating head 10 and that in this manner the effective stroke of the ram may be increased or decreased.

circular die 20 cooperates with the ram 12 to perform the dishing operation. When it is desired to dish plates which are relatively large in size the circular die 20 has a 24 inches, and the upper sur face thereof is dished out on a curvature of 42 inches radius. The stroke of the ram 12 during the'dishing operationis adjusted so that the end of the ram just reaches the bottom of the die 20. In order to safeguard the machine, if for any reason the ram should be lengthened out too much, a hole 20 is provided, of sufficient size to permit clearance of the ram, should the latter be forced therein. h

In order to dish small plates, it is not necessary to employ a large die, and for tlns purpose I have found that a die 12 inches in diameter, and whose upper surface is curved on a shorter radius, gives the best results.

In the operation of dishing a plate, the ram 12 is first adjusted in the reciprocating head 10' so that when the head is at the lower end of its stroke, the end of the ram 12 projects slightly below the plane of the upper edge of the die 20. The press is then operated to lift the ram out ofthe die and a flat plate is inserted between the ram and the die in such position that the edge of the plate coincides with the edge of the die 20, and a portion thereof is directly under the ram, as for example the portion 30 in Fig. 2.

this i that a ten foot circular The press is "then operated to force down the ra'm and to raise it agaminto an inoperative position, in this manner de ressing ortion of the sheet and pro ucing a circu ar depression in the plate near its periphery'. The plate is then moved until a second portion 31 lies over the d1e and the operation is repeated. Similar depressions are successively made in this manner in eac of the adjacent portions of the plate such as 32, 33, 34, 35, 36, 37, 38, in Fig. 2. After the portion of the plate near the periphery has been depressed, a second set of portions of the plate 41, 42, 43, 44, 45, 46, 47 48, are then subjected to a similar cycle of operations producing depressions of the same depth as the first series of depressions. After the completion of the second cycle of operations the plate is moved thereunder so that the central portion of the plate comes under the ram and a central portion 49 is depressed.

he positions of successive depressions with relation to one another are such that the plate is dished in a uniform curve, an after completion of the operation the plate assumes a perfectly formed dished shape,

and the irregularlties of the individual depressions are blended to form a continuous curvature from near the periphery of the plate to the center.

A sweep is used as a gage in order to ob tain the proper curvature, and if in the completion of the initial dishing operation, the curvature of the dish is not sufiicient, the complete operation is repeated with the ram 12 lengthened out slightly so as to form deeper individual depressions.

It will be observed that only two operators are needed to dish a plate, one to operate the press and one to hold the plate, 50

plate may be dishe ina relatively short time. I have found that such a plate may be dished in from one to two hours, so that the total expense incurred does not amount to more than five dollars which compares favorably with the expense of sixty dollars which dishing at the mill incurs.

While I have described the preferred emh of the plate to bodiment of the invention it is not desired to limit the invention, as modifications thereof may be had within the scope of the following claims:

1. The method of cold dishing circular metal plate having the characteristics of boiler plate which consists in successively depressing and stretching different portions form a circular dish of uniform curvature, whereby the diameter of the circular plate remains substantially unaltered.

2. The method of cold dishing metal plate having the characteristics of boiler plate which consists in successively subjectin different portions of the plate to the com ined stretching and depressing action of a ram and die to form a dish of uniform curvature.

3. The method of cold dishing metal plate having the characteristics of boiler plate which consists in successively subjecting adjacent portions of the plate to the combined stretching and depressing action of a cylindrical ram and a circular die having a d dished surface of materially greater diamethe ram, to form a ter than the diameter of dished plate of uniform curvature.

4. The method'of cold dishing metal plate having the characteristics of boiler plate which consists in subjecting difierent portions of the plate to the combined stretching and depressing action of a cylindrical ram and a circular die having a dished surface of materially greater diameter than the diameter of the ram, said portions being concentrically arranged with respect to the center of the plate and at different distances therefrom.

5. The method of cold dishing metal plate having the characteristics of boiler plate which consists in successively depressing 1 different portions of the plate an equal amount and in such manner as to slightly stretch the material thereof to form a dish of uniform curvature, said portions being arranged to overlap slightly and in circular paths concentrically arranged with respect to the center of the plate.

HUGH MQGABE. 

